Beverage bottle containers currently have two piece caps where one of the pieces, typically the outer piece or hard cap, predominantly contains polypropylene, and the other piece, typically the inner piece or liner, predominantly contains an ethylene-vinyl acetate (EVA) copolymer. Polypropylene is relatively inexpensive, tough, dense, and moldable, but can be challenging to process without a relatively high degree of processing additives. Without the relatively high degree of processing additives, the polypropylene cannot typically be processed effectively into beverage bottle caps. These processing additives, in a single piece polypropylene beverage bottle cap, can and often do leach out into the beverage contained in the beverage bottle, thus contaminating the beverage and causing undesirable organoleptic properties.
Thus, one reason that two piece beverage bottle caps have been used is to gain the sealability and positive organoleptic properties of the low density EVA liner, while simultaneously retaining the other physical properties of polypropylene without exposing the beverage to the polypropylene processing additives. However, two piece beverage bottle caps can be expensive and difficult to process, particularly because of the relatively high cost of the EVA copolymer resin and the complications of a multi-step fabrication process.
The present invention seeks to solve these problems by utilizing unique multimodal polyethylene polymers and/or resins that advantageously need lower levels of leachable additives to attain processing efficiency and yet simultaneously exhibit both relative strength and density sufficient for the physical demands of the application. As a result, single piece beverage bottle caps can be made from these unique polymers/resins.